The invention relates generally to arthroplasty and, more particularly, to devices and techniques for positioning a prosthesis.
During the implantation of bowed orthopedic hip implants with fixed neck-bow orientation, there exists a tendency for the implant to rotate or corkscrew as it enters the bow of the femur. This causes an undesirable implant neck orientation otherwise referred to as neck version (hereafter, simply referred to as “version”). Currently available bowed modular implants do not address this situation as they are assembled outside the body with the version set based on trials prior to implementation. A variety of external assembly devices have been developed that set the final implant in the same version as that determined during trial (see, e.g., the Sundial Version Control device available from Biomet, Inc.).
In addition, the surgeon must estimate the degree of implant rotation and begin the implantation in an undesirable orientation with the expectation that the implant will be properly orientated at the completion of implantation. If optimal implant neck version is not attained, the surgeon must decide whether to leave the implant in a non-optimal orientation and risk possible dislocation, or extract the implant and re-implant.